Alyson Lee Hannigan (born March 24, 1974) is an American actress. Her most notable roles are as Willow Rosenberg on Buffy the Vampire Slayer (1997–2003), Lily Aldrin on How I Met Your Mother (2005–2014), and Michelle Flaherty in the American Pie film series (1999–2012).
Hannigan started acting at a young age, moving to Hollywood when she was just 11 years old to pursue her career. She was cast in her first major film role for the film My Stepmother Is an Alien (1988) alongside Seth Green, who later joined her in the regular cast of Buffy. Hannigan eventually married her Buffy co-star Alexis Denisof in 2003. The couple live in Encino with their two daughters, Satyana Marie and Keeva Jane.